The Microbiology of Turfgrass Soils

Most turfgrass managers do not have a strong understanding of turfgrass soils, particularly the biological aspects. Certainly most know that living things, such as worms and insects can reside in soil, but they’re not sure where in the soil they live or what they live on. In fact, it might be safe to assume that most turfgrass managers consider soil to be a mysterious world below the turfgrass canopy. Rarely do turfgrass managers consider soil as something that should be managed as prudently as the turf itself. It is becoming clear, however, that the management of the soil, in particular its biological components, is perhaps as important as the management of the plant for the long-term productivity and health of a turfgrass stand. Most soils below turfgrass stands contain a vast array of living organisms, ranging from the larger macroscopic earthworms and insects, to the microscopic invertebrates, bacteria, fungi, actinomycetes, nematodes, algae, and protozoa. The types, numbers, and activities of these organisms directly and indirectly impact on turfgrass health. Most turfgrass managers are familiar with the harmful effects that some microorganisms have on turfgrass health. For example, these damaging microorganisms include fungal, bacterial, and nematode pathogens of turfgrass plants, cyanobacteria—a form of blue-green algae that causes black layer, and green algae that cause surface crusting and plant damage. There are other groups of microorganisms that are indirectly harmful to turfgrass plants. These include pesticide-degrading non-pathogenic and pesticide-resistant pathogenic microorganisms. In nearly all cases, turfgrass managers have developed elaborate management techniques to avoid some of the detrimental effects caused by the activities of these organisms. Despite the presence of harmful microorganisms in turfgrass soils, most soils contain large populations of beneficial microorganisms. These offer the most promise for enhancing turfgrass health and maintaining long-term productive turfgrass stands (Table 1).